Connect4K with AI. Run this as applet.

N.java

import java.applet.Applet;
import java.awt.AWTEvent;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.event.KeyEvent;
import java.awt.image.BufferedImage;
import java.util.Arrays;


public class N extends Applet implements Runnable{
	private static final int CELL = 50, COL = 6, ROW = 8, WIDTH = CELL * COL, HEIGHT = CELL * ROW + CELL;
	private static final int[] blank_0 = {-1, -1, -1, -1, -1, -1};
	
	private int x = -1, y = -1, vm = -1, lastX = -1;
	private boolean m = false, human = true, first = true, q = false;
	private int[] up = new int[COL];
	private int[][] v;
	
	public void start(){
		new Thread(this).start();
	}

	@Override
	public void run() {
		// TODO Auto-generated method stub
		final int dy = 300;
		setSize(new Dimension(WIDTH, HEIGHT));
		enableEvents(AWTEvent.KEY_EVENT_MASK);
		requestFocus();
		while(true){
			x = y = vm = lastX = -1;
			m = q = false; 
			human = first = q = true;
			v = new int[COL][ROW];
			Arrays.fill(up, ROW - 1);
			long a =0;
			int t = 0, fps = 0, i = 0, r = 0, win_v = -1;
			boolean win = false;
			first = true;
			BufferedImage b = new BufferedImage(WIDTH, HEIGHT, BufferedImage.TYPE_INT_RGB);
			Graphics2D g = (Graphics2D)b.getGraphics();
		    Graphics p = getGraphics();
		    
		    for (long d = 0, start = System.nanoTime(); q; d = System.nanoTime() - start, start = System.nanoTime()){
				a += d;
				t++;
				if (a >= 1000000000L) {
				   a -= 1000000000L;
				   fps = t;
				   t = 0;
				}
				
				if (!win){
					if (m){
						y += d * dy / 1000000000L;
						if (y >= up[x] * CELL){
							if (vm == 1) lastX = x;
							m = false;
							v[x][up[x]] = vm;
							up[x]--;
							if (checkWin(vm)){
								win_v = vm;
								win = true;
							}
							x = y = vm = -1;
							human = !human;
							if (Arrays.equals(up, blank_0)){
								win = true;
								win_v = 1;
							}
						}
					}else{
						if (!human){
							m = true;
							if (lastX == COL / 2 - 1){ //2 (3)
								if (first){
									x = COL / 2;
									first = false;
								}else{
									x = lastX;
								}
							}else if (lastX == COL / 2){ //3 (4)
								if (first){
									x = COL / 2 - 1;
									first = false;
								}else{
									x = lastX;
								}
							}else{ // follow-up
								x = lastX;
							}
							if (up[x] < 0){
								for (i=0; i<up.length; i++){
									if (up[i] % 2 == 0){ //ganjil
										x = i;
										break;
									}
								}
							}
							y = 0;
							vm = 2;
						}
					}
				}
				
				g.setColor(Color.black);
				g.fillRect(0, 0, WIDTH, HEIGHT);
				g.setColor(Color.DARK_GRAY); //background
				g.fillRect(0, 0, WIDTH, HEIGHT - CELL);
				for (i=1; i<=COL; i++)
					g.drawString(String.valueOf(i), i * CELL - 30, HEIGHT - 20);
				g.setColor(Color.black);
				for (i=1; i<ROW; i++)
					g.drawLine(0, i * CELL, WIDTH, i * CELL);
				for (i=1; i<COL; i++)
					g.drawLine(i * CELL, 0, i * CELL, HEIGHT);
				for (i=0; i<COL; i++){
					for (r=0; r<ROW; r++){
						if (v[i][r] != 0){
							g.setColor((v[i][r]==2)? Color.black : Color.white);
							g.fillOval(i * CELL, r * CELL, CELL, CELL);
						}
					}
				}
				if (m){
					g.setColor((vm == 2)? Color.black : Color.white);
					g.fillOval(x * CELL, y, CELL, CELL);
				}
				g.setColor(Color.red);
				g.drawString("FPS " + String.valueOf(fps), 10, HEIGHT - 5);
				g.drawString("press 9 to restart", 200, HEIGHT - 5);
				if (win){
					g.setColor(Color.green);
					if (win_v == 1){
						g.drawString("DRAW!", WIDTH /2 - 50, HEIGHT - 5);
					}else{
						g.drawString(((win_v == 2)? "BLACK" : "WIN").concat(" HAS WIN!"), WIDTH /2 - 50, HEIGHT - 5);
					}
				}
				
				p.drawImage(b, 0, 0, null);
				try { 
					Thread.sleep(2L); 
				} catch (Exception e) {}
				if (!isActive())
					return;
		    }
		}
	}
	
	private boolean checkWin(int v1){
		boolean ret = false;
		for (int r=0; r<2; r++)
			for (int i=0; i<5; i++)
				if (v[r][i] == v1 && v[r+1][i+1] == v1 && v[r+2][i+2] == v1 && v[r+3][i+3] == v1) ret = true;
		if (!ret)
			for (int r=COL-1; r>COL-3; r--)
				for (int i=0; i<5; i++)
					if (v[r][i] == v1 && v[r-1][i+1] == v1 && v[r-2][i+2] == v1 && v[r-3][i+3] == v1) ret = true;
		if (!ret)
			for (int r=0; r<ROW; r++)
				for (int i=0; i<COL/2; i++)
					if (v[i][r] == v1 && v[i+1][r] == v1 && v[i+2][r] == v1 && v[i+3][r] == v1) ret = true;
		if (!ret)
			for (int r=0; r<COL; r++)
				for (int i=0; i<=ROW-4; i++)
					if (v[r][i] == v1 && v[r][i+1] == v1 && v[r][i+2] == v1 && v[r][i+3] == v1) ret = true;
		return ret;
	}
	
	public void processEvent(AWTEvent e){
		if (e.getID() == KeyEvent.KEY_RELEASED){
			int k = ((KeyEvent) e).getKeyCode();
			if (k == 57)
				q = false;
			if (k >= 49 && k<=54 && !m){
				x = (k - 49);
				if (up[x] >= 0){
					m = true;
					y = 0;
					vm = 1;
				}
			}
		}
	}

}